A "traditional" hotel will (should) have a proper "bookings/reservation" procedure a "modern" one may well rely entirely on booking.com or similar.

Moreover it depends on the "incentives" (or lack thereof) of the actual people at the reception, in large hotels (or chains of hotels) why employee/clerk - say - #215 (possibly a low paid intern) would want to actually work to make your reservation (as you can do it yourself online, less work and responsibilities for him/her).

If you think a bit about it, when you book on one of these sites, you take all responsibilities about dates (arrival departure) people (number of people in each room) types of rooms (like two/three bed, queen size or king size bed, etc.) type of accomodation (with/without breakfast).

It is not entirely uncommon that people arrives on the "wrong" date or has miscalculated the days of stay (rare but happens from time to time), or - this happens quite often - having booked a single use room for two people or similar, simply because of a slip on the finger or not having read the whole page of info on the accomodation.

If you write or (when possible better) talk with the reception, usually they can verify your request and offer you more options (like - say - a "family room" for 4 people instead of two doubles, or a room with a large balcony if you are traveling with a pet).

In this case, you can contact the hotel and ask for a better offer. Works sometimes.